As is conventionally known, a connector is attached to, for example, separators of a fuel cell to detect the voltage of power generation by respective cells of the fuel cell. When the connector is connected with the fuel cell, displacement of the insertion direction of the connector to the fuel cell or misalignment of the insertion position of the connector to the fuel cell may cause bad connection or damage of the fuel cell. In order to solve this problem, one proposed technique provides a protruded guide member on one of the connector and the fuel cell and a recessed groove on the other of the connector and the fuel cell and slides the connector to be connected with the fuel cell while the guide member is fit in the groove (PTL1).